The present invention relates to a bookbinding apparatus, and in particular, to a bookbinding apparatus that prepare booklets by bonding a plurality of sheets with adhesive.
In the field of light printing, for example, image forming systems are being used widely that prepare booklets from printing to bookbinding in one process by coupling an image forming apparatus having the ability to form images at a high speed such as an electro-photographic image forming apparatus, and a bookbinding apparatus.
Although such image forming systems have low printing speed and low bookbinding speed when compared with the conventional book manufacturing process in which the printing process and the bookbinding process are executed as separate processes, they have the advantage that it is possible to change the content of printing at any time and are on the whole high efficiency image forming systems, and are being used as POD (Print On Demand) systems.
Since a POD system has the image forming apparatus and the bookbinding apparatus coupled to each other, and is not installed in a factory for printing and bookbinding but is very often installed either within an office or in the same building as the office, it has to be small in size, and all parts constituting the system are required to be small in size.
Therefore, even as a bookbinding apparatus is used the type that prepares booklets by binding bundling sheets using adhesive bonding which is a relatively simple process.
A reduced size bookbinding apparatus has been disclosed in Unexamined Japanese Patent Application Publication No. 2000-168265 that prepares a booklet by coating the adhesive by moving the coating roller relative to the longitudinal direction of the spine of the sheet bundle by moving the sheet bundle with respect to the coating roller.
In Unexamined Japanese Patent Application Publication Nos. 2004-209746 and 2004-276457 are disclosed, in a coating apparatus suitable for small-sized bookbinding apparatus, an adhesive replenishing device that carries out replenishment of adhesive at an accurate rate in a simple manner.
In Unexamined Japanese Patent Application Publication Nos. 2004-209746 and 2004-276457 is proposed a replenishing member that transports pellets of adhesive material along an inclined transport path, and by opening or closing a threshold member provided in the transport path, supplies a fixed quantity of pellets of about a few pellets during each replenishment.
In a reduced size adhesive coating apparatus, since the level of the adhesive liquid in the adhesive reservoir varies widely because the volume of the adhesive reservoir that contains the liquid of the adhesive material is small, not only it is required to carry out replenishment of the adhesive accurately but also it is necessary to control the rate of replenishment according to the thickness of the sheet bundle, and a replenishment control that has accuracy and speed is required.
When a replenishment mechanism is used that replenishes in units of a few pellets as in Unexamined Japanese Patent Application Publication Nos. 2004-209746 and 2004-276457, although the replenishment control is carried out by controlling the number of replenishments in units of a few pellets, there was the problem that the accuracy of the replenishment in this type of replenishment control is not sufficient, and also, that the speed of control of meeting speedily the changes in the quantity of adhesive and it was difficult to carry out uniform coating over a long period.
In other words, when there is any disturbance in the unit of replenishment, because the inaccurate replenishment is carried out repeatedly, the replenishment error gets accumulated leading to the condition of excessive or insufficient quantity of adhesive in the adhesive reservoir.